Device for feeding a drying gas to a mixing granulator

ABSTRACT

The invention relates to a device for feeding a drying gas to a mixing granulator comprising a mixing chamber and a rotating agitator ( 3 ), on which mixer blades ( 4 ) are arranged in a radial position with respect to a drive shaft ( 5 ). The feeder line ( 6 ) for the drying gas is disposed inside the drive shaft ( 5 ) of the agitator ( 3 ). An exit line ( 7 ) is respectively connected in the region of each mixer blade ( 4 ), said line terminating in at least one outlet ( 8 ) arranged underneath and, in the direction of rotation, behind the mixer blades (s). The outlet ( 8 ) extends advantageously in at least partial manner along the mixer blades ( 4 ), embodied in the form of a slit or in a flat manner in the form of a porous element.

This is a nationalization of PCT/DE02/02036 filed May 31, 2002 andpublished in German.

The invention relates to a device for feeding a drying gas to a mixinggranulator with a mixing chamber and a rotating agitator, on which mixerblades are arranged in a radial position with respect to a drive shaft.

In a mixing granulator such as this, a powder and a liquid binding agentare added to and mixed in the mixing chamber while the agitator rotates.The result is a dough-like mass as the mixed product, which isimmediately crushed into granulate-like particles by means of amechanically operating crusher. As a result, the granulate-likeparticles are dried to granulate that can be handled by the agitator bymeans of a drying gas during the agitation. Modern mixing granulatorsoperate at high efficiencies, whereby an adequately high amount ofdrying gas must be fed into, and discharged back out of the mixingchamber in the time unit.

According to prior art, several different solutions are known of feedingdrying gas into the mixing chamber. Among others, EP 385 956 B1 providesa device for the production of bulk material in the shape of balls ofsmall diameters, made of a finely pulverized material. Ground bladesrotate around a vertical axis in a boiler, and means for the supply andextraction of gas, or of a gas mixture, are present. For feeding thegas, a ring-shaped porous wall is provided at the bottom of the boiler,which is arranged in a radial position in the area of a porous lowersurface of the ground blades. The drying gas entering in a flat mannerthrough the bottom of the mixing chamber is therefore directedunderneath the ground blades.

A mixing granulator is described in JP 50 49 901 A, in which an agitatorwith a vertical axis, as well as mixer blades are arranged at the bottomof the mixing granulator. The central part of the agitator is embodiedlike a bell, whereby the mixer blades essentially are attached at thebottom. Via a gas feeder line, drying gas can be fed into the upper areaof the bell-shaped rotor component, and flows toward the bottom alongthe interior wall, until it enters the chamber of the mixing granulatorin the area of the mixer blades.

The invention is based on the task of providing a device for feeding adrying gas to a mixing granulator of the above described type, whichenables the effective feeding of a larger amount of a drying gas.

The invention performs the task by means of the characteristics statedin the representative part of claim 1. Advantageous further embodimentsof the invention are characterized in the sub-claims, and, together withthe description of the preferred embodiment of the invention, includingthe drawing, are explained in detail as follows.

The invention essentially consists of the fact that the drying gas isfed across the axis of the agitator, and that each of the mixer bladeshas an exit line, which has at least one outlet arranged underneath andin the direction of the rotation, behind the mixer blades.

By integrating the feeder line into the rotor axis, the feeding of thedrying gas occurs at a minimal requirement of space and without anyseparate gas lines. The outlet of the drying gas occurs into the spacethat is essentially free of granulate, as the same is tossed toward thetop at the front surfaces of the mixer blades. The drying gas therebyflows in a wide area through the granulate, which is again falling tothe bottom due to the dispersion, and can thereby discharge moisturefrom the granulate in a markedly effective manner. The solutionaccording to the invention thereby also particularly enables theeffective feeding of very large amounts of drying gas.

The practical embodiment of the outlet is possible in different ways,for example in accordance with claims 2 to 4. Accordingly, the outletsextend at least partially along the length of the mixer blades. This canbe embodied in the form of simple slits, or in the form of porouselements. The goal of the individual solutions is to create planeoutlets. In so far as separate outlets are used, it is beneficial toconnect the respective elements to the exit line via quick-releasefasteners that are known as such.

Generally, the invention is not restricted to a particular position ofthe axis, or suspension of the agitator. However, it has been provenadvantageous to arrange the axis of the agitator vertical to a mixinggranulator with a static cover and a mixing chamber that can be loweredvertically. In such a mixing granulator, all other elements, such as thefeeder lines for the base materials of the granulate to be produced, therequired crusher, and the suction line for the drying gas can also bearranged on the static cover. The mixing chamber that can be loweredvertically is then completely free of technically required assemblycomponents, and can, for example, advantageously be emptied and cleaned.

The special advantage of the invention is that a large amount of dryinggas can be fed across the axis of the agitator without any separatefeeder lines, and introduced in a plane manner underneath the agitatinggranulate into the mixing chamber by means of the outlets according tothe invention.

The invention is further explained in detail by means of an embodimentexample, as follows.

The drawing shows a partial section across a mixing granulator with adevice for feeding a drying gas according to the invention.

The mixing granulator consists of a housing 1, a cover 2, and anagitator 3 supported in the cover 2. The housing 1 is embodied with twowalls, and the temperature can be maintained by means of a fluid. Thecover 2 is statically arranged within a rack that is not illustrated,and the housing 1 can be lowered vertically toward the bottom.

In the operating position illustrated, the agitator 3 is lowered intothe housing 1, and only a minimal gap necessary for construction designpurposes exists on the bottom of the housing 1 between both elements.

The agitator 3 essentially consists of a drive shaft 5, and three radialmixer blades 4 arranged on it. The rotary drive of the agitator 3 islocated above the cover 2, and is not illustrated in the drawing.

For the feeding of the drying gas into the mixing chamber, a feeder line6 is embodied in the drive shaft 5 of the agitator 3. The feeder line 6terminates at the bottom in the drive shaft 5, and, in the area of themixer blades 4, is divided into one exit line 7 assigned to each of themixer blades 4. The exit lines 7 terminate at the outlets 8, which arelocated in the direction of rotation of the drive shaft 5 behind themixer blades 4. In the embodiment example, the outlets 8 are embodied inthe shape of cartridges from a porous sintered body. The cartridges arescrewed into the exit line 7. The attachment can also be realized bymeans of quick-release fasteners, such as bayonet catches.

The technologically additionally required elements for a mixinggranulator are exclusively arranged on the cover 2 in the embodimentexample. They include the merely principally indicated elements crusher9, feeder devices 10 for the base materials, and a gas discharge line11.

During the operation of the device according to the invention, a dryinggas is fed via the feeder line 6. The gas flow is divided at the lowerend of the drive shaft 5 into three individual flows within the exitlines 7, and enters in a wide area into the mixing chamber via the threecartridges embodied as the outlets 8. The entry into the mixing chamberoccurs in the direction of rotation behind and below the mixer blades 4in tunnel-shaped chambers within the rotating granulate. From there, thedrying gas flows in a wide area through the rotating granulate, absorbsmoisture from the granulate at a great efficiency rate, and dischargesit from the mixing chamber via the gas discharge line 11.

Of course, the invention is not limited to the embodiment exampledescribed. It is possible without any problems to embody the agitatordifferently, for example with other mixer blades; to arrange the axis ofthe drive shaft in a different position, or to change the outlet.Several feeder lines may also be embodied in the axis of the agitator.This invention also includes any solutions, in which not every one ofthe existing mixer blades has an outlet, such as when the said bladesare present on several levels.

LIST OF REFERENCE SYMOBOLS USED

-   1 housing-   2 cover-   3 agitator-   4 mixer blades-   5 drive shaft-   6 feeder line-   7 outlet-   8 exit line-   9 crusher-   10 feeding device-   11 gas discharge line

1. Device for feeding a drying gas to a mixing granulator with a mixingchamber and a rotating agitator (3), on which mixer blades (4) arearranged in a radial position with respect to a drive shaft (5),characterized in that a feeder line (6) for the drying gas is disposedinside the drive shaft (5) of the agitator (3), to which one exit line(7) each is connected in the area of each mixer blade (4), and that eachexit line (7) has at least one outlet (8) underneath and, in thedirection of the rotation, behind the mixer blades (4).
 2. Deviceaccording to claim 1, characterized in that the outlet (8) extends atleast partially along the length of the mixer blades (4).
 3. Deviceaccording to claim 2, characterized in that the outlet (8) is embodiedin the form of a slit.
 4. Device according to claim 2, characterized inthat a porous element is present as the outlet (8), via which the dryinggas can exit in a flat manner.
 5. Device according to claim 1,characterized in that the outlet (8) is connected to the exit line (7)by means of a known quick-release fastener.
 6. Device according to claim1, characterized in that the mixing granulator has an upper static cover(2), and a housing (1) that can be lowered vertically, and that theagitator (3) is supported on the vertical axis in the cover (2). 7.Device according to claim 6, characterized in that, as an additionaltechnical device, at least a crusher (9) and/or feeder lines (10) forthe base material, and/or a discharge line (11) for the drying gas areprovided on the cover (2).